Automotive finishing methods include metallic color finishing and solid color finishing. The former method commonly comprises applying a metallic base coat and then further applying a clear coat thereon by the wet-on-wet method followed by thermal curing, namely, a two-coat one-bake system. Since an acryl melamine resin coat is employed as the clear coat, the coating thus obtained is poor in, for example, acid resistance and staining resistance. Thus it has been required to overcome these disadvantages.
In the case of the solid color finishing, on the other hand, a one-coat one-bake system is generally employed with the use of an alkyd melamine resin coat. Recently, it has been required to improve the appearance of the finished coating and to enhance properties thereof such as weathering resistance, acid resistance and staining resistance. In order to satisfy these requirements, the application of a clear coat on a solid color has been proposed. However no satisfactory coating material has been obtained so far by this method.
Known thermal cured coats (for example, acryl melamine and alkyd melamine) employed in various coatings for, for example, the exterior of architectural structures, automobiles, industrial machines, steel furniture, appliances and plastics contain melamine as a crosslinking agent. Thus these coats suffer from an unsolved problem, namely, the odor of the melamine resin.